This is an update from a previous post: https://www.camaroz28.com/forums/sho...d.php?t=747145

I broke down and got a new Delphi opti from the Partsladi and EXACTLY the same result.

Now for what is important: datalogging shows something interesting with a WOT run:

On the right bank , I go lean pretty much from about 4K RPM on up. The 02 does not ever get back to where it should be (about 900 mv) and instead will fluctuate. Then my left bank goes slightly lean at about 6K. This corresponds with the car sputtering in this RPM range.

So, going lean shows 3 possible issues:

the injectors are not working correctly at higher loads and temperatures (I have my old 24's and will install these tomorrow with a reflash).

the spark plugs are incorrect for the application (they are brand new BTW)

Plug wires bad. (highly doubt this since both banks ultimately were affected)

Regarding the spark plugs, 96AZHawk suggested I called AFR and they indicated a different plug than what I had in there. They suggested the Autolite 3924 (flat and washer .75 reach) and I have the 103 (taper .708 reach). I will be getting new plugs tomorrow.

Has anyone heard that plugs can cause miss issues if the incorrect ones are installed?

 

Just tried some header wrap close to the fuel lines. There was a VERY slight change in miss but still it was there. Again, data confirmed that I am going intermittently lean in the right bank somewhere after 4500 RPM.

Once the car cools down, I will do an injector change.

 

OK, NOW THINGS ARE GETTING FREAKY!!!!!!!!

I was going to replace the injectors with my old 24lb and while doing so, I notice that the current injectors had junk in them. Specifically, cylinder 2 and 8 (right bank) had enough to plug 1/3 of the flow. further, cylinder 1 had quite a bit in it (left bank). OK, so I think this is solved and so I take it out for a test drive.

WOT run, coolant temps mid 220's and datalogging. At 4300 RPM, the 02's go from rich and even at 890 mV and then both banks together drop drop within 0.4 seconds to extremely lean, around 60 mV. Even though I am in PE mode, the computer trys to compensate by adding fuel but this make no difference in the 02's and they stay around 60 mV. It is at this point that I start getting the same issues I have had before of sputtering.

WTF is going on?!

 

check compression ?slight head gasket leak.

 

Can you check the fuel pressure under load - when the O2s drop? One possibility is fuel vaporization in the inlet side of the pump, if your fuel is heating up. (You said in another post to think outside the box).

 

PROBLEM FINALLY SOLVED!!!

Well not completely but I have generated a solution. Here is what was happening:

I am running VE so part of the equation is the IAT. Well, because of location, I was seeing that the IAT would get heat soaked. Higher IAT means less air thus I would be lean because the computer was compensating by reducing fuel. the IAT was indicating a temperature of about 50-60 F above ambient.

OK, I move the IAT to the front of the cold air box. Now the IAT is a few degrees from ambient and try again. Still the same problem but I go lean later in the RPM range so I assume I gained some fuel there.

Next what I did was add fuel in the upper RPM range for PE mode using "%change FAR vs. RPM at WOT" in Tunercat. This pretty much eliminated my problem and I have not ever felt this car this strong! I suppose I have always been lean. Thank god I have forged pistons.

Here is the odd thing however, I had to add like 50% additional fuel in the FAR vs RPM table up top but only got a 15% increase in the PCM's BPW. I had to do this as compared to just redoing my whole VE table because I was at 100% VE already at around 5000 RPM which is way short of my goal of 6600. the PCM will not go above 100% in the table.

My next step is to lower my injector constant 10% and recalibrating my VE table thus giving me room up top to correctly calibrate the table. Any other suggestions?

Thanks all for their help!

 

Thanks for the input and yesterday I wrapped the header area close to my fuel lines. A slight difference but it was not the whole solution but I have not checked the fuel pressure at the higher temps I have been testing at. I will do that this week.

Ben